Dear all
We realized that our posterior-anterior (PA) epi sequence for susceptibility correction is not an exact copy (but for the PE direction) of the AP epi we want to correct.
these are the different parameters:
GOOD_PA sequence (exact copy of the EPI_AP epi we want to correct, with PE direction inverted)
"EchoTime": 0.033,
"RepetitionTime": 0.72,
"FlipAngle": 52,
"RefLinesPE": 12,
"MultibandAccelerationFactor": 8,
"EchoTrainLength": 90,
"BandwidthPerPixelPhaseEncode": 19.157,
"EffectiveEchoSpacing": 0.000580003,
"DerivedVendorReportedEchoSpacing": 0.000580003,
"TotalReadoutTime": 0.0516202,
BAD_PA sequence
"EchoTime": 0.058,
"RepetitionTime": 7.06,
"FlipAngle": 90,
"RefLinesPE": 24,
"EchoTrainLength": 45,
"BandwidthPerPixelPhaseEncode": 42.735,
"ParallelReductionFactorInPlane": 2,
"EffectiveEchoSpacing": 0.00026,
"DerivedVendorReportedEchoSpacing": 0.000520001,
"TotalReadoutTime": 0.02314
I applied topup with both PA versions (setting the two proper TotalReadOutTime).
After visual inspection, they seem to similarly and succesfully correct for the A->P stretching. but since they are very different sequences (e.g. EPI_AP and GOOD_PA are multiband, BAD_PA not and different TR/ET ) I'm not sure I can do it .
do you have any suggestion?
thanks in advance
Alberto
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